The recycling of different materials and the conversion of the energy contents of waste or biomass becomes ever more relevant and the target of large scale investments, private as well as public. The procedure used normally is to pre-sort those materials found in the municipal waste, which may be recycled. What remains are materials that may be converted into energy through, for example, incineration.
The problem of waste accumulation grows steadily. It is expensive both in terms of collection costs and fees charged, and it is particularly unacceptable in terms of the valuable resources that are wasted.
Incineration is a common method for retrieving energy from waste that cannot be recycled. The energy is usually converted into heat in the form of hot water or steam that subsequently may replace “nobler” forms of energy.
Hierarchically, electricity in the form of alternating current is the most valuable form of energy, as it may, at low cost, be converted into practically any other form of energy.
The cost of converting the energy contents of waste into electric power through incineration is, however, very high, usually requiring large plants if conversion is to yield a good financial return. The high costs are the result particularly of very strict public regulations regarding the release of polluting emissions into the atmosphere.
Pyrolysis is known traditionally as the conventional retort dry distillation process utilizing an external source of heat, sometimes combined with partial combustion of the contents in the retort. Examples of such processes are the production of wood-tar/charcoal and coke from wood and coals respectively. In modern plants, pyrolysis may be best known as what the petrochemical industry refers to as “cracking.”
Even after the invention of the magnetron in 1921, which used radio tubes to create the microwaves (MW), it took a quarter of a century before MW generators reached the market and came into practical use. In the post-WWII period, MW processes have found multiple applications within industries and in private households.